Rinse lentils under cold water until water runs clear, drain. Pick out any discoloured lentils or stones and discard.Heat oil in frying pan. Add onion, garlic and ginger and sauté until onion softens. Add all the spices and chilli and cook stirring until fragrant – about 1 minute. Add the stock and bring the mixture to the boil.Pour the spiced stock mixture into the slow cooker and stir in chicken, undrained tomatoes, lentils and pumpkin. Cover and cook on low for 7 hours.Stir in coconut milk. Turn heat to high and cook covered for 15 minutes, stirring once. Stir in spinach and coriander.